Engine test bench temperature control system

Abstract

The application discloses an engine test bench temperature control system, which comprises a main circulating water pipeline, a cooling liquid cooling branch, an oil cooling branch, a dynamometer auxiliary cooling branch and a intercooler auxiliary cooling branch connected in parallel to the pipeline; the cooling liquid cooling branch and the oil cooling branch are connected to a preheating unit through a three-way valve respectively; the preheating unit comprises a cooling liquid preheater and an oil preheater arranged in parallel, and both are heated by a shared heating water tank; an electric heater is arranged in the heating water tank and connected with an exhaust heat exchanger, which is connected with the cooling liquid preheater and the oil preheater through an electric three-way proportional shunt valve respectively. The application can integrate all cooling functions, simplify the structure, reduce the cost, and efficiently utilize the engine full working condition exhaust waste heat, realize "exhaust heating as the main, electric heating as the auxiliary", so as to meet the actual needs of engine performance test in the laboratory scene.

Description

Technical Field

[0001] This invention relates to a temperature control device, and more particularly to a temperature control system for an engine test bench. Background Technology

[0002] With the rapid development of the national economy, transportation industry, and automotive industry, the internal combustion engine, as the core power source for road transportation and construction machinery, is becoming increasingly important in terms of performance testing and technological research and development. Especially at the current stage of parallel development of new energy and traditional fuel power, the efficient combustion, clean emissions, and reliability testing of internal combustion engines cannot be separated from the support of high-precision, stable, and controllable test benches. As the core equipment for internal combustion engine performance research and development, fault diagnosis, and parameter calibration, engine test benches place higher demands on the integration, stability, and economy of fluid temperature control and auxiliary cooling systems. Simultaneously, under the dual-carbon development trend, the energy efficiency of the system has also become an important design indicator.

[0003] During engine testing, the temperature stability of the coolant and engine oil directly determines the cylinder block thermal load, lubrication performance, and combustion efficiency, thus affecting the accuracy and repeatability of experimental data. Simultaneously, auxiliary equipment such as the dynamometer and intercooler require a continuous and stable supply of cooling water to prevent overheating damage and ensure precise control of intake air temperature, guaranteeing the smooth conduct of the experiment. Furthermore, the engine continuously emits combustion exhaust gases throughout its operating cycle. The characteristics of exhaust gases vary significantly under different operating conditions. While the exhaust gases during the start-up phase possess some heat, their low temperature, small flow rate, and large fluctuations in operating conditions limit their quality and quantity, making effective utilization difficult. Therefore, a highly efficient, compact, low-cost temperature control and cooling system that also utilizes waste heat is an indispensable core component of the engine test bench.

[0004] Currently, in the field of engine test benches, existing temperature control systems generally adopt the traditional approach of "multiple independent systems set up separately," and a dedicated integrated solution for laboratory scenarios has not yet been formed. Furthermore, there is a significant technological gap in the utilization of exhaust waste heat. Specifically, engine coolant temperature control, oil temperature control, water-cooled dynamometer cooling, and intercooler cooling all use their own independent systems, each equipped with dedicated circulation, temperature control, and control components, forming independent piping and equipment systems. Regarding the exhaust waste heat generated by the engine, existing technologies only make simple use of the high-temperature stable exhaust gas during normal operation in some engineering application scenarios. Utilization of exhaust gas during the start-up phase is limited, especially during steady-state test start-up. Due to its characteristics of temperature fluctuations of 150-250℃, and large fluctuations in gas volume, pressure, and temperature, the exhaust gas is considered to have low utilization value and is directly discharged without being fully utilized. However, the heat from the exhaust gas in this temperature range actually fully meets the hot water heating requirements for preheating the test bench medium, resulting in considerable energy waste.

[0005] The aforementioned traditional separate solutions, coupled with the lack of waste heat utilization in exhaust gas, have brought about several prominent pain points, severely restricting the utilization rate of laboratory space and the economy, energy efficiency, and practicality of experimental benches: First, there is serious equipment redundancy. The coolant and oil temperature control systems require two independent heating water tanks, circulating pumps, and control components. The dynamometer and intercooler also require independent water circuits and valves, resulting in high procurement and maintenance costs. Second, the space required is large. The cross-laid piping of multiple independent systems leads to a significant reduction in laboratory space utilization, and the complex piping is prone to failure, making troubleshooting and maintenance difficult. Third, energy consumption is high. The simultaneous operation of two independent heating water tanks easily leads to heat waste, and the parallel operation of multiple systems increases overall energy consumption. The waste heat from the exhaust gas during the start-up phase is directly wasted. During the warm-up phase of the experimental bench, the heat is entirely provided by the electric heating device. Electric heating becomes the main means of preheating rather than an auxiliary measure, which further exacerbates the energy consumption problem. Fourth, there is redundancy in the metering components. The existing solution is to equip all branches with flow meters, which not only further increases the equipment cost but also increases the pipeline resistance and affects the temperature control response speed. Fifth, the waste heat utilization is disconnected from the temperature control system. The existing technology does not combine the utilization of waste heat from the exhaust gas with the dual-medium temperature control of the experimental bench. It has neither designed a suitable heat exchange device for the unstable exhaust gas at medium and low temperatures during the start-up and idling phase, nor has it combined the small-scale utilization of waste heat from the exhaust gas with medium heating during normal operation. It is impossible to reduce the electric heating load by heating the exhaust gas.

[0006] As internal combustion engine test benches develop towards miniaturization, integration, low cost, and energy efficiency, the shortcomings of traditional multiple independent temperature control and cooling systems, coupled with the industry problem of underutilization of exhaust waste heat, are becoming increasingly prominent. There is an urgent need for an integrated solution that can integrate all temperature control and cooling functions, simplify the structure, reduce costs, and efficiently utilize engine exhaust waste heat to achieve "exhaust gas heating as the main method and electric heating as a supplement" to meet the actual needs of engine performance testing in laboratory settings. Summary of the Invention

[0007] This invention provides an engine test bench temperature control system to solve the technical problems existing in the prior art. The system can integrate all cooling functions, simplify the structure, reduce costs, and efficiently utilize the exhaust heat of the engine under all operating conditions to achieve "exhaust gas heating as the main method and electric heating as the auxiliary method" to meet the actual needs of engine performance testing in laboratory scenarios.

[0008] The technical solution adopted by this invention to solve the technical problems existing in the prior art is as follows: an engine test bench temperature control system, including a main circulating water pipeline, and a coolant cooling branch, an oil cooling branch, a dynamometer auxiliary cooling branch, and an intercooler auxiliary cooling branch connected in parallel to the pipeline; the coolant cooling branch and the oil cooling branch are respectively connected to a preheating unit through a three-way valve; the preheating unit includes a coolant preheater and an oil preheater arranged in parallel, both of which are heated by a common heating water tank; the heating water tank is equipped with an electric heater and connected to an exhaust gas heat exchanger, which is connected to the coolant preheater and the oil preheater respectively through an electric three-way proportional flow divider valve;

[0009] The temperature control system uses a controller, and the steps are as follows:

[0010] S1: System Initialization and Status Detection

[0011] After the system starts, the controller obtains the following data by collecting sensor data at each node in real time: medium temperature: oil temperature T6, coolant temperature T7; heat source status: water temperature at the outlet of the heating water tank T8, exhaust gas inlet temperature of the exhaust gas heat exchanger T12, exhaust gas outlet temperature of the exhaust gas heat exchanger T11; set targets: coolant target temperature Tc_set, oil target temperature To_set.

[0012] S2: Rapid preheating upon startup

[0013] When the actual oil temperature T6 is lower than the trigger point for starting rapid heating or the actual coolant temperature T7 is lower than the trigger point for starting rapid heating, rapid preheating is used. Specific methods include:

[0014] S21: Heat source selection

[0015] Electric heating mode: When the exhaust gas temperature T12 is detected to be less than the waste heat utilization start threshold or the engine is not running, it is determined that there is no waste heat available, the electric heater is turned on, and the power is set to 100%;

[0016] Mixed transition mode: When the waste heat utilization start threshold ≤ T12 ≤ waste heat sufficient threshold, the exhaust gas proportional regulating valve is opened to introduce waste heat, and the power of the electric heater is reduced proportionally to carry out mixed heating;

[0017] Pure waste heat mode: When T12 > waste heat sufficient threshold, it is determined that the waste heat of the exhaust gas is sufficient. At this time, the electric heater is turned off and the opening of the exhaust gas proportional regulating valve is adjusted to make full use of the waste heat to heat the water in the heating water tank to the set temperature.

[0018] S22: Media path switching:

[0019] Initially, the three-way valve is in the cooling position. When the preheating unit starts, it needs to be switched to the straight-through position so that the engine oil and coolant can flow into the engine after exiting the preheating unit.

[0020] S23: Dual-medium synchronous control: Calculate the temperature difference ΔTgap = (To_set - T6) - (Tc_set - T7). If ΔTgap > 0, the engine oil is severely underheated. Adjust the electric three-way proportional flow divider valve inside the preheating unit to increase the proportion of hot water flowing into the engine oil preheating branch to ensure that both media reach the target temperature simultaneously.

[0021] S3: Steady-state constant temperature operation stage

[0022] When both T7 and T6 are within their respective target ranges for stopping heating, the system enters the cooling and constant temperature maintenance phase. Specific methods include:

[0023] S31: Stops the heating water tank from supplying heat to the coolant preheater and oil preheater;

[0024] S32: Switch the two three-way valves to the cooling position so that the engine oil and coolant can each enter their respective coolers for cooling.

[0025] S4: Shutdown protection and preheating elimination

[0026] After the experiment ends, the system enters the shutdown protection process: the main circulating water pump continues to run, and the three-way valves corresponding to the coolant cooling branch and the oil cooling branch remain in the cooling position, controlling the coolant cooling branch and the oil cooling branch to continue running until the oil temperature and coolant temperature at the engine outlet drop to a safe temperature, and then all branches are closed.

[0027] Based on the above solution, the present invention has made the following improvements:

[0028] Step S3 further includes S33: Cooling intensity adjustment: A pneumatic regulating valve and a flow meter are installed on the water supply pipe of the coolant cooler. The controller adjusts the opening of the pneumatic regulating valve in real time according to the feedback from the flow meter using a PID algorithm to control the circulating water flow.

[0029] Temperature and pressure sensors are installed at both the inlet and outlet of the oil cooling branch. A manual ball valve and a pneumatic regulating valve are installed sequentially on the water supply pipe of the cooler. The cooling effect is indirectly judged by the temperature difference between the inlet and outlet of the branch and the feedback data from the pressure sensor. It works in conjunction with the coolant cooling branch to achieve dual-medium temperature control.

[0030] The system's oil cooling circuit is sequentially equipped with a pressure sensor, a temperature sensor, a liquid reservoir, a variable frequency pump, a pressure stabilizing tank, a preheater, and a three-way valve. The three-way valve is connected to the oil cooling branch. A pneumatic regulating valve is installed on the water supply pipe of the oil cooling branch. In step S32, the oil temperature control adopts a dual regulation strategy of variable frequency pump speed and pneumatic regulating valve opening: the variable frequency pump speed is increased first; if the temperature continues to rise, the pneumatic regulating valve opening is further increased.

[0031] In step S32, when the medium reaches the target range for stopping heating, the three-way valve switches from the straight-through position to the cooling position, and at the same time, each branch variable frequency pump automatically compensates for the flow fluctuation caused by the path switching according to the temperature rise slope.

[0032] The advantages and positive effects of this invention are:

[0033] This system addresses a series of pain points associated with discrete temperature control systems in engine test benches, including equipment redundancy, high energy consumption, insufficient temperature control accuracy, and poor reliability. It proposes a highly integrated, intelligent, and efficient thermal management solution. Its core innovations and advantages are as follows:

[0034] 1. Highly integrated architecture, significantly reducing costs and increasing efficiency.

[0035] To address the issues of redundant equipment, large footprint, and high life-cycle costs in traditional discrete systems, this invention adopts a "multi-branch integration + core component sharing" topology, integrating multiple circuits such as coolant, engine oil, and dynamometer into a single common trunk line and sharing a closed preheating unit. This significantly reduces the number of hardware components such as pumps, valves, and sensors, directly lowering procurement and maintenance costs. At the same time, it compresses bench space and solves the laboratory layout problem.

[0036] 2. Indirect cascade waste heat recovery, balancing energy saving and reliability.

[0037] A two-stage buffer heat exchange mode of "exhaust gas-hot water-medium" is proposed, using a hot water tank as a buffer to isolate exhaust gas pollution; it follows an intelligent energy supply logic of "exhaust gas as the main source and electric auxiliary heating as a supplement." This solves the problems of high energy consumption during cold starts, waste of exhaust gas waste heat, and easy carbon buildup and corrosion from direct heat exchange. It fundamentally avoids the risk of exhaust gas coking and blockage, resulting in a long hardware lifespan; it recovers low-grade waste heat, enabling rapid cold starts and significantly reducing system operating energy consumption.

[0038] 3. Asymmetric heat flow distribution enables synchronous warm-up of heterogeneous media.

[0039] Based on the thermal properties of the media, an asymmetrical and precise flow distribution is implemented for the two media streams through a three-way proportional valve and dynamic distribution algorithm inside the preheater. This allocates more heat flow to the slower-heating oil side, ensuring that the oil and coolant can reach the set temperature synchronously and quickly, significantly shortening the experimental preparation time. This solves the problem of asynchronous heating between oil and coolant due to their different specific heat capacities, which slows down the experimental process.

[0040] 4. Decoupled closed-loop control achieves high-precision temperature control and "zero-interference" switching.

[0041] The decoupled control strategy of "variable frequency pump flow closed loop + PID regulating valve" is adopted. During the switching transient, the pump speed and valve position are pre-adjusted to offset the disturbance caused by the change of flow path. The steady-state accuracy of oil and coolant temperature is ≤±1℃ under all working conditions, and the mode switching is smooth, which greatly ensures the repeatability and accuracy of experimental data.

[0042] 5. Intelligent redundancy and safety design enhance the inherent reliability of the system.

[0043] The system employs an intelligent sensing configuration combining direct monitoring of core branches with model calculations for non-core branches. It also incorporates safety logic for automatic pressure relief and waste heat dissipation during shutdown. While ensuring a closed-loop control system, this reduces system flow resistance and power consumption, completely eliminating pipe coking or air pockets caused by heat buildup during shutdown, thus ensuring long-term stable operation. It eliminates flow resistance and potential failure points caused by redundant flow meters and prevents the risk of localized overheating after shutdown. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the structure of the present invention;

[0045] Figure 2 This is a schematic diagram of the preheating unit in this invention.

[0046] In the diagram: 1-Main circulation water inlet manual ball valve, 2-Y-type filter, 3-Main flow meter, 4-Oil branch manual ball valve, 5-Oil branch pneumatic regulating valve, 6-Oil cooler, 7-Coolant branch manual ball valve, 8-Pneumatic regulating valve, 9-Flow meter, 10-Coolant cooler, 11-Dynamometer branch manual ball valve, 12-Intercooler branch manual ball valve, 13-Oil reservoir, 14-Variable frequency pump, 15-Pressure tank, 16-Preheating unit, 17-Oil three-way valve, 1 8-Coolant reservoir, 19-Variable frequency pump, 20-Pressure stabilizing tank, 21-Coolant three-way valve, 22-Heating water tank, 23-Electric shut-off valve, 24-Variable frequency hot water pump, 25-Pressure stabilizing tank, 26-Electric three-way proportional flow divider valve, 27-Coolant preheater, 28-Oil preheater, 29-Exhaust gas heat exchanger, 30-Exhaust gas proportional regulating valve, T1-T12 are the temperatures of the corresponding nodes, measured by temperature sensors, P1-P8 are the pressures of the corresponding nodes, measured by pressure sensors. Detailed Implementation

[0047] To further understand the invention's content, features, and effects, the following embodiments are provided, and detailed descriptions are given below in conjunction with the accompanying drawings:

[0048] Addressing the main shortcomings of existing technologies, the core objective of this invention is to provide an integrated dual-medium temperature control and cooling system and control method for engines based on exhaust waste heat utilization. This breaks through the limitations of traditional discrete architectures by integrating various temperature control and cooling branches and sharing a single hot water heat source that primarily uses exhaust waste heat for heating and is supplemented by electric heating. This fundamentally solves the core pain points of equipment redundancy, large footprint, and high cost. Simultaneously, it adapts to the exhaust gas characteristics during engine start-up by designing dedicated heat exchange and flow control logic, fully utilizing exhaust waste heat to reduce system energy consumption. Furthermore, it designs a precise collaborative control strategy based on the thermal characteristics differences between coolant and engine oil, improving the accuracy of dual-medium temperature control. Ultimately, this results in a compact, energy-efficient, and precisely temperature-controlled integrated temperature control and cooling system for laboratory use, meeting the actual needs of engine test benches.

[0049] Please see Figure 1 and Figure 2 A temperature control system for an engine test bench includes a main circulating water pipeline and a coolant cooling branch, an oil cooling branch, a dynamometer auxiliary cooling branch, and an intercooler auxiliary cooling branch connected in parallel to the pipeline.

[0050] The coolant cooling branch and the oil cooling branch are respectively connected to the preheating unit 16 through a three-way valve 21 and 17; the preheating unit 16 includes a coolant preheater 27 and an oil preheater 28 arranged in parallel, both of which are heated by a common heating water tank 22; the heating water tank is equipped with an electric heater and is connected to the exhaust gas heat exchanger 29, which is connected to the coolant preheater 27 and the oil preheater 28 respectively through an electric three-way proportional flow divider valve 26.

[0051] The temperature control system uses a controller, and the steps are as follows:

[0052] S1: System Initialization and Status Detection

[0053] After the system starts, the controller obtains the following data by collecting sensor data at each node in real time: medium temperature: oil temperature T6, coolant temperature T7; heat source status: water temperature at the outlet of the heating water tank T8, exhaust gas inlet temperature of the exhaust gas heat exchanger T12, exhaust gas outlet temperature of the exhaust gas heat exchanger T11; set targets: coolant target temperature Tc_set, oil target temperature To_set.

[0054] S2: Rapid preheating upon startup

[0055] When the actual oil temperature T6 is lower than the trigger point for starting rapid heating or the actual coolant temperature T7 is lower than the trigger point for starting rapid heating, rapid preheating is used. Specific methods include:

[0056] S21: Heat source selection

[0057] Electric heating mode: When the exhaust gas temperature T12 is detected to be less than the waste heat utilization start threshold or the engine is not running, it is determined that there is no waste heat available, the electric heater is turned on, and the power is set to 100%;

[0058] Mixed transition mode: When the waste heat utilization start threshold ≤ T12 ≤ waste heat sufficient threshold, the exhaust gas proportional regulating valve is opened to introduce waste heat, and the power of the electric heater is reduced proportionally to carry out mixed heating;

[0059] Pure waste heat mode: When T12 > waste heat sufficient threshold, it is determined that the waste heat of the exhaust gas is sufficient. At this time, the electric heater is turned off and the opening of the exhaust gas proportional regulating valve 30 is adjusted to make full use of the waste heat to heat the water in the heating water tank 22 to the set temperature.

[0060] S22: Media path switching:

[0061] Initially, the three-way valves 17 and 21 are in the cooling position. When the preheating unit 16 is started, it needs to be switched to the straight-through position so that the engine oil and coolant can flow directly into the engine after coming out of the preheating unit 16.

[0062] S23: Dual-medium synchronous control: Calculate the temperature difference ΔTgap = (To_set - T6) - (Tc_set - T7). If ΔTgap > 0, the engine oil is severely underheated. Adjust the electric three-way proportional flow divider valve 26 inside the preheating unit 16 to increase the proportion of hot water flowing into the engine oil preheating branch to ensure that the two media reach the target temperature at the same time.

[0063] S3: Steady-state constant temperature operation stage

[0064] When both T7 and T6 are within their respective target ranges for stopping heating, the system enters the cooling and constant temperature maintenance phase. Specific methods include:

[0065] S31: Stop the heating water tank 22 from supplying heat to the coolant preheater 27 and the oil preheater 28;

[0066] S32: Switch the two three-way valves 17 and 21 to the cooling position so that the engine oil and coolant can enter the corresponding coolers 6 and 10 for cooling.

[0067] S4: Shutdown protection and preheating elimination

[0068] After the experiment ends, the system enters the shutdown protection process: the main circulating water pump continues to run, and the three-way valves 17 and 21 corresponding to the coolant cooling branch and the oil cooling branch remain in the cooling position, controlling the coolant cooling branch and the oil cooling branch to continue running until the oil temperature and coolant temperature at the engine outlet drop to a safe temperature, and then all branches are closed.

[0069] The concept of this invention is based on an "indirect thermal energy coupling architecture": the system realizes the transfer and distribution of energy through a preheating unit, which integrates an exhaust gas heat exchanger and an electric heating water tank.

[0070] To address the unstable exhaust gas temperature and the presence of oily particles during engine start-up, this invention abandons the traditional approach of directly heating the exhaust gas medium, instead employing an indirect heat exchange mode of "exhaust gas / electricity—hot water—engine oil / coolant." Utilizing a closed-loop hot water circuit as a heat buffer, it achieves a green heat source supply mode of "exhaust gas heating as the primary method and electric heating as a secondary method" during start-up. This solves the problem of exhaust gas oil contamination of the heat exchanger and enables cascaded energy utilization. Simultaneously, it integrates engine coolant and engine oil temperature control branches with auxiliary cooling branches for the dynamometer and intercooler, breaking away from the traditional multi-system discrete architecture. This addresses the pain points of existing technologies, such as equipment redundancy, high cost, large footprint, high energy consumption, and waste of exhaust gas heat, achieving integrated, energy-saving, and precise temperature control for engine test bench temperature control and cooling functions. The auxiliary cooling branches for the dynamometer and intercooler are connected in parallel to the main circulation pipeline via a three-way valve and an electric regulating valve, with the controller adjusting the flow rate of each branch to meet its different cooling requirements.

[0071] The preferred solution is as follows:

[0072] The above step S3 also includes S33: Cooling intensity adjustment: A pneumatic regulating valve 8 and a flow meter 9 are installed on the water supply pipe of the coolant cooler 10. The controller adjusts the opening of the pneumatic regulating valve 8 in real time according to the feedback of the flow meter 9 using a PID algorithm to control the circulating water flow.

[0073] Temperature and pressure sensors are installed at both the inlet and outlet of the oil cooling branch. A manual ball valve 4 and a pneumatic regulating valve 5 are installed sequentially on the water supply pipe of the cooler 6. The cooling effect is indirectly judged by the temperature difference between the inlet and outlet of the branch and the feedback data from the pressure sensor. It works in conjunction with the coolant cooling branch to achieve dual-medium temperature control.

[0074] The system's oil circuit is sequentially equipped with a pressure sensor, a temperature sensor, a reservoir 13, a variable frequency pump 14, a pressure stabilizing tank 15, a preheater 16, and a three-way valve 17. The three-way valve 17 is connected to the oil cooling branch. A pneumatic regulating valve 5 is installed on the water supply pipe of the oil cooling branch. In step S32, the oil temperature control adopts a dual regulation strategy of "variable frequency pump speed" and "pneumatic regulating valve opening": prioritizing the increase of the variable frequency pump 14 speed; if the temperature continues to rise, the opening of the pneumatic regulating valve 5 is further increased.

[0075] In step S32, when the medium reaches the target range for stopping heating, the three-way valves 17 and 21 switch from the straight-through position to the cooling position, and at the same time, each branch variable frequency pump automatically compensates for the flow fluctuation caused by the path switching according to the temperature rise slope.

[0076] The invention will be described in more detail below with reference to examples:

[0077] The layout of each branch of the above system is as follows:

[0078] 1) Main circulating water pipeline

[0079] The main circulating water is divided into four branches after passing through manual ball valve 1, Y-type filter 2, and main flow meter 3: oil cooling branch, coolant cooling branch, dynamometer cooling branch, and intercooler cooling branch. Finally, they converge into the "main circulating water outlet", providing a common cooling water source for the entire system.

[0080] 2) Oil cooling branch

[0081] This branch is an auxiliary temperature control branch, with a manual ball valve 4, a pneumatic regulating valve 5, and a cooler 6 arranged in sequence. No additional flow meter is configured. The cooling effect is indirectly judged by the temperature difference between the inlet and outlet of the branch and the feedback data from the pressure sensor, which effectively reduces equipment cost and pipeline complexity. It works in conjunction with the coolant cooling branch to achieve dual-medium temperature control.

[0082] 3) Coolant cooling branch

[0083] This branch is the core temperature control branch of the engine. It is arranged with a manual ball valve 7, a pneumatic regulating valve 8, a flow meter 9, and a cooler 10 in sequence. Through the closed-loop control of the pneumatic regulating valve and the flow meter, the coolant flow rate is precisely adjusted to ensure that the coolant temperature is stable within the target range, ensuring uniform heat load on the engine block and improving the accuracy of experimental data.

[0084] 4) Auxiliary cooling branch (dynamometer / intercooler)

[0085] The dynamometer branch and intercooler branch are equipped with only manual ball valves 11 and 12. The cooling effect is indirectly judged by pressure switches and temperature sensors, eliminating the need for flow meters, thus simplifying the structure and reducing costs.

[0086] 5) Engine closed-loop circuit (coolant / engine oil)

[0087] This circuit is divided into a coolant closed-loop circuit and an oil closed-loop circuit, achieving independent circulation and coordinated temperature control of the two media:

[0088] 5.1) Closed-loop oil circuit: The oil enters the preheating unit through the reservoir 13, variable frequency pump 14, and pressure stabilizing tank 15. The flow direction is switched by the temperature control three-way valve 17. In the preheating mode, it goes directly to the engine lubrication system, and in the cooling mode, it enters the oil cooler 6 to cool down.

[0089] 5.2) Coolant closed loop: The coolant enters the preheating unit 16 through the reservoir 18, variable frequency pump 19, and pressure stabilizing tank 20. The flow direction is switched by the temperature control three-way valve 21. In the preheating mode, it flows directly to the engine block. In the cooling mode, it enters the coolant cooler 10 to cool down.

[0090] Both loops are linked to the hot water heat exchanger of the preheating unit, prioritizing the use of waste heat from the exhaust gas for preheating, ensuring a coordinated increase in the temperature of both media.

[0091] 6. Preheating Unit

[0092] This unit is the core module for dual-medium preheating and exhaust gas waste heat utilization. It mainly uses exhaust gas heating and is supplemented by electric heating. The components are, in order: hot water tank 22, electric shut-off valve 23, variable frequency hot water pump 24, pressure stabilizing tank 25, three-way proportional diverter valve 26, coolant preheater 27, engine oil preheater 28, exhaust gas shell-and-tube heat exchanger 29, exhaust gas electrically controlled proportional valve 30, and various temperature and pressure monitoring components.

[0093] During the start-up phase, exhaust gas heating is the primary method, supplemented by electric heating, providing a stable heat source for dual-medium preheating and adapting to the unstable characteristics of exhaust gas volume, pressure, and temperature. During normal engine operation, the coolant and engine oil primarily function for cooling; exhaust gas does not enter the preheating unit, and the hot water in the preheating unit is not circulated, ceasing to supply heat to the coolant and engine oil.

[0094] This invention presents a schematic diagram of the overall structure of an engine dual-medium integrated temperature control and cooling system based on exhaust waste heat utilization. It mainly includes a main circulating water pipeline, coolant cooling branches, engine oil cooling branches, auxiliary cooling branches (dynamometer and intercooler cooling), an engine oil closed-loop circuit, an engine coolant closed-loop circuit, and a preheating unit interface. All branches are integrated and connected, sharing core control components to achieve integrated temperature control and cooling functions. An exhaust gas inlet channel is also provided for linkage with the exhaust gas heat exchange device of the preheating unit. Heating during engine start-up is achieved by the preheating unit, with an internal proportional regulating valve controlling the flow rate of hot water for heat exchange between the engine oil and coolant, adapting to the different heating energy required for both to reach their set temperatures. Cooling during normal operation is achieved by adjustable flow rate heat exchangers on the engine oil and coolant branches.

[0095] System operation strategy and working mode

[0096] The core control of this system lies in its ability to smoothly switch between three energy regulation methods—electric heating, exhaust waste heat, and active cooling—based on the engine's real-time status. The standard coolant temperature is set at 80℃, and the standard engine oil temperature at 90℃. The detailed control steps are as follows:

[0097] 1. System initialization and status detection

[0098] After the system starts up, the controller collects data from various sensors in real time: medium temperature: engine oil temperature T6, coolant temperature T7.

[0099] Heat source status: Preheating unit outlet water temperature T8, exhaust gas inlet temperature T12. Target settings: Coolant target temperature Tc_set = 80℃, engine oil target temperature To_set = 90℃.

[0100] 2. Rapid preheating stage

[0101] When T7 < 78℃ or T6 < 88℃ is detected, the system is determined to be in preheating mode.

[0102] 2.1 Heat source selection logic:

[0103] If T12 < 100℃ (engine not ignited or cold), turn on the electric heater (22) in the preheating unit. Set the power to 100%.

[0104] If T12 > 150℃ and T11 - T12 > 50℃, the heat source is deemed effective. The electric heater is gradually shut off, and the exhaust gas proportional regulating valve is opened (initially 80%) to use the residual heat to heat the water in the hot water tank.

[0105] 2.2 Medium path switching: When the temperature control three-way valves 17 and 21 are switched to the straight-through position, the engine oil and coolant do not pass through the coolers 6 and 10, but flow directly to the preheater 16 for heat exchange.

[0106] 2.3 Dual-medium synchronous control: Calculate the temperature difference ΔTgap = (To_set - T6) - (Tc_set - T7).

[0107] If ΔTgap>0, it indicates that the engine oil is severely underheated. Adjust the three-way proportional flow divider valve inside the preheating unit to increase the proportion of hot water to the engine oil preheating branch, ensuring that both media reach the target temperature simultaneously.

[0108] 3. Steady-state constant temperature operation stage

[0109] When T7 reaches 80±1℃ and T6 reaches 90±1℃, the system switches to cooling and constant temperature maintenance mode:

[0110] 3.1 Preheating unit unloading: Close the electric shut-off valve 23 of the preheating unit, stop the hot water pump 24, and switch the tail gas proportional regulating valve to the bypass position.

[0111] 3.2 Cooling circuit activation: Temperature control three-way valves 17 and 21 are switched to the cooling position, and the medium enters coolers 6 and 10.

[0112] 3.3 Precision adjustment of cooling intensity:

[0113] Coolant circuit: The controller uses a PID algorithm to adjust the opening of the pneumatic regulating valve 8 in real time based on the feedback from the flow meter 9, thereby controlling the circulating water flow.

[0114] Oil circuit: Considering that the viscosity of oil is greatly affected by temperature, a dual regulation of "variable frequency pump speed + pneumatic regulating valve opening" is adopted. When T6>90.5℃, the variable frequency pump speed 14 is increased first; if the temperature continues to rise, the opening of the pneumatic regulating valve 5 is increased.

[0115] 4. Shutdown protection and preheating elimination

[0116] After the experiment ends and the command is triggered:

[0117] 4.1 Forced Cooling: Keep variable frequency pumps 14 and 19 running, lock the temperature control three-way valve at the maximum cooling position, and continue supplying main circulating water. Continue for 15-20 minutes until the engine outlet temperature drops below 50°C.

[0118] 4.2 System Interlock: Shut down all active power sources (pumps, heaters) and return pneumatic valves to safe positions.

[0119] Although preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other modifications under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these modifications are within the scope of protection of the present invention.

Claims

1. A temperature control system for an engine test bench, characterized in that, This includes the main circulating water pipeline, as well as the coolant cooling branch, engine oil cooling branch, dynamometer auxiliary cooling branch, and intercooler auxiliary cooling branch connected in parallel to the pipeline; The coolant cooling branch and the engine oil cooling branch are each connected to the preheating unit through a three-way valve; the preheating unit includes a coolant preheater and an engine oil preheater arranged in parallel, both of which are heated by a common heating water tank; the heating water tank is equipped with an electric heater and connected to the exhaust gas heat exchanger, which is connected to the coolant preheater and the engine oil preheater respectively through an electric three-way proportional flow divider valve; The temperature control system uses a controller, and the steps are as follows: S1: System Initialization and Status Detection After the system starts, the controller obtains the following data by collecting sensor data at each node in real time: medium temperature: oil temperature T6, coolant temperature T7; heat source status: water temperature at the outlet of the heating water tank T8, exhaust gas inlet temperature of the exhaust gas heat exchanger T12, exhaust gas outlet temperature of the exhaust gas heat exchanger T11; set targets: coolant target temperature Tc_set, oil target temperature To_set. S2: Rapid preheating upon startup When the actual oil temperature T6 is lower than the trigger point for starting rapid heating or the actual coolant temperature T7 is lower than the trigger point for starting rapid heating, rapid preheating is used. Specific methods include: S21: Heat source selection Electric heating mode: When the exhaust gas temperature T12 is detected to be less than the waste heat utilization start threshold or the engine is not running, it is determined that there is no waste heat available, the electric heater is turned on, and the power is set to 100%; Mixed transition mode: When the waste heat utilization start threshold ≤ T12 ≤ waste heat sufficient threshold, the exhaust gas proportional regulating valve is opened to introduce waste heat, and the power of the electric heater is reduced proportionally to carry out mixed heating; Pure waste heat mode: When T12 > waste heat sufficient threshold, it is determined that the waste heat of the exhaust gas is sufficient. At this time, the electric heater is turned off and the opening of the exhaust gas proportional regulating valve is adjusted to make full use of the waste heat to heat the water in the heating water tank to the set temperature. S22: Media path switching: Initially, the three-way valve is in the cooling position. When the preheating unit starts, it needs to be switched to the straight-through position so that the engine oil and coolant can flow into the engine after exiting the preheating unit. S23: Dual-medium synchronous control: Calculate the temperature difference ΔTgap = (To_set - T6) - (Tc_set - T7). If ΔTgap > 0, the engine oil is severely underheated. Adjust the electric three-way proportional flow divider valve inside the preheating unit to increase the proportion of hot water flowing into the engine oil preheating branch to ensure that both media reach the target temperature simultaneously. S3: Steady-state constant temperature operation stage When both T7 and T6 are within their respective target ranges for stopping heating, the system enters the cooling and constant temperature maintenance phase. Specific methods include: S31: Stops the heating water tank from supplying heat to the coolant preheater and oil preheater; S32: Switch the two three-way valves to the cooling position so that the engine oil and coolant can each enter their respective coolers for cooling. S4: Shutdown protection and preheating elimination After the experiment ends, the system enters the shutdown protection process: the main circulating water pump continues to run, and the three-way valves corresponding to the coolant cooling branch and the oil cooling branch remain in the cooling position, controlling the coolant cooling branch and the oil cooling branch to continue running until the oil temperature and coolant temperature at the engine outlet drop to a safe temperature, and then all branches are closed.

2. The engine test bench temperature control system according to claim 1, characterized in that, Step S3 further includes S33: Cooling intensity adjustment: A pneumatic regulating valve and a flow meter are installed on the water supply pipe of the coolant cooler. The controller adjusts the opening of the pneumatic regulating valve in real time according to the feedback from the flow meter using a PID algorithm to control the circulating water flow.

3. The engine test bench temperature control system according to claim 2, characterized in that, Temperature and pressure sensors are installed at both the inlet and outlet of the oil cooling branch. A manual ball valve and a pneumatic regulating valve are installed sequentially on the water supply pipe of the cooler. The cooling effect is indirectly judged by the temperature difference between the inlet and outlet of the branch and the feedback data from the pressure sensor. It works in conjunction with the coolant cooling branch to achieve dual-medium temperature control.

4. The engine test bench temperature control system according to claim 1, characterized in that, The system's oil cooling circuit is sequentially equipped with a pressure sensor, a temperature sensor, a liquid reservoir, a variable frequency pump, a pressure stabilizing tank, a preheater, and a three-way valve. The three-way valve is connected to the oil cooling branch. A pneumatic regulating valve is installed on the water supply pipe of the oil cooling branch. In step S32, the oil temperature control adopts a dual regulation strategy of variable frequency pump speed and pneumatic regulating valve opening: the variable frequency pump speed is increased first; if the temperature continues to rise, the pneumatic regulating valve opening is further increased.

5. The engine test bench temperature control system according to claim 1, characterized in that, In step S32, when the medium reaches the target range for stopping heating, the three-way valve switches from the straight-through position to the cooling position, and at the same time, each branch variable frequency pump automatically compensates for the flow fluctuation caused by the path switching according to the temperature rise slope.

Images