Laboratory ventilation system for multi-supercharger successive supercharged engine and optimization design method

Abstract

The invention provides a test room ventilation system for a multi-supercharger successive supercharged engine, which comprises air supply pipes arranged at two ends of the engine, and the tail ends of the air supply pipes penetrate out of a test room and are provided with first outdoor fans; a switching valve is arranged between the tail end, located outside the test chamber, of the air supply pipe and the first outdoor fan and electrically connected with a PLC control box, so that the air supply pipe is automatically opened and closed according to the operation condition of the engine. The method for designing and calculating the ventilation flow according to the rated power of the engine is provided, and reasonable distribution of the combustion demand and the heat dissipation demand air supply amount is achieved; through simulation calculation, the air supply arrangement form is determined, airflow is effectively organized, and it is ensured that air enters each supercharger at the temperature close to the outdoor environment while the good heat exchange effect is achieved; the overall ventilation flow is adjusted according to the test working condition, independent air supply of the air inlet area is involved according to the working state of the supercharger, the similar ventilation effect is maintained under different test working conditions, and energy saving is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of engine testing, and in particular to a test room ventilation system and an optimization design method for a multi-supercharger sequential supercharging engine. Background Art

[0002] In actual application of high-power marine diesel engines, the design of cabin air intake is mostly adopted, which is conducive to providing stable intake temperature and air quality for diesel engine superchargers and extending the service life of diesel engines. The ventilation system scheme of cabin air intake must be arranged with special cabin blowers and ventilation ducts. The air supply flow rate should be sufficient to cover the engine combustion and cabin equipment heat dissipation requirements, and the air volume should be reasonably distributed. In order to truly reflect the working state of cabin air intake, during the test verification phase of the newly developed high-power sequential supercharged high-speed diesel engine, the test laboratory also adopted the indoor air intake scheme and designed a ventilation system with a flow rate that meets the engine combustion and laboratory heat dissipation. In addition, the high-speed diesel engine intake system adopts a multi-supercharger sequential supercharging method to meet the fresh air required for the high and low operating conditions of the engine. Multiple superchargers are arranged above the entire engine body. During the test, each supercharger is started successively as the operating conditions increase. On the one hand, the design of the ventilation system should ensure that the intake temperature of each supercharger is consistent as much as possible to avoid affecting the engine's performance; on the other hand, when the superchargers are started one after another, the test laboratory's requirements for ventilation flow will also be different when the engine runs under different operating conditions.

[0003] For multi-supercharger indoor intake engine test chambers, conventional ventilation systems have the following disadvantages:

[0004] The ventilation main pipe is arranged in a bottom-intake and top-exhaust form, without distinguishing between air supply for ventilation and air supply for combustion. The temperature of fresh air rises after blowing through the engine body from a low position and is discharged upwards. However, since the supercharger adopts an indoor air intake method and is installed on the top of the engine, the high-temperature air after heat exchange will be directly sucked into the engine, resulting in high intake temperature, which affects the engine's working performance.

[0005] In the test laboratory environment, there are patrol platforms, auxiliary system equipment, pipelines and other facilities around the engine that affect the ventilation flow field, making the indoor temperature field distribution uncontrollable, resulting in large differences in the intake temperature of the supercharger installed at different positions of the engine, affecting the test performance;

[0006] The number of times the supercharger works varies with the engine's operating conditions. Under low operating conditions, the ventilation volume required for heat dissipation and air intake is small, and the system cannot provide indoor air supply conditions that are targeted at the operating conditions. A constant ventilation flow rate can easily lead to a waste of electricity. Summary of the invention

[0007] In response to the problems existing in the prior art, the present application proposes a test laboratory ventilation system for a multi-supercharger sequentially supercharged engine, comprising an air supply duct arranged at both ends of the engine, wherein the ends of the air supply duct pass through the test laboratory and are provided with a first outdoor fan; a switching valve is provided between the end of the air supply duct outside the test laboratory and the first outdoor fan, and the switching valve is electrically connected to a PLC control box to realize automatic opening and closing of the air supply duct according to the operating conditions of the engine.

[0008] Furthermore, the air supply duct is divided into two layers, the lower layer air supply is fully open, and the upper layer air supply is automatically opened and closed according to the engine operating conditions.

[0009] Furthermore, the upper air supply of the air supply duct is divided into left and right compartments, respectively aimed at the air inlets of the superchargers on both sides of the engine; the lower air supply of the air supply duct is not divided into compartments, and is aimed at the engine body below the supercharger.

[0010] Furthermore, it also includes an exhaust duct on the top of the test building, and a second outdoor fan is arranged in the exhaust duct on the top of the test building.

[0011] The design method of the above system comprises the following steps:

[0012] Lower air supply calculation: The lower air supply is used to purge the engine body to achieve ventilation and heat exchange;

[0013] Upper air supply calculation: The upper air supply duct is used to meet the air intake demand of the supercharger on the top of the engine;

[0014] Calculate the overall air volume and design two outdoor variable frequency blowers to supply air to the air supply pipe at one end of the engine;

[0015] Estimation of ventilation system effectiveness.

[0016] Furthermore, the calculation of the lower-level air supply specifically includes:

[0017] Assume that the rated power of the engine is P [kW], and the total power of heat dissipation to the test room is φ = 0.1P [kW]. Under rated conditions, the heat dissipation power is a constant value; heat dissipation is achieved through convection and thermal radiation:

[0018] Total heat dissipation power: Φ=Φ1+Φ2

[0019] Convective heat transfer power: Φ1=hA(T1-T2)

[0020] Radiative heat transfer power: Φ2=εAσ(T1 4 -T2 4 )

[0021] The convective heat transfer coefficient h increases mainly with the increase of air flow velocity, while the radiation heat transfer power is determined by the surface temperature of the diesel engine; if the h value is increased by increasing the flow velocity, φ1 will increase and φ2 will decrease;

[0022] The width of the lower air outlet is greater than the width of the engine, and the height is designed to be 1 / 2 of the height of the engine body;

[0023] The purge air volume at one end of the engine is q≥100φ[m 3 / h], the air velocity when blowing to the engine body is v≥7m / s, the air supply duct is designed to be inclined downward at 45°, and the air flow along the center line of the air supply port should be blown directly to the height center of the engine body.

[0024] Furthermore, the upper air supply calculation specifically includes:

[0025] Assume that the number of superchargers is n, the number of upper air supply pipe openings is also n, and the number of upper air supply pipe openings at one end of the engine is n / 2. The air intake demand of a single supercharger at room temperature is A[m 3 / h], that is, the flow rate of a single air supply pipe on the upper layer q'≥A[m 3 / h];

[0026] The total width of the upper air supply duct is consistent with that of the lower one, the air outlet interval is 0.05-0.1m, and the air outlet height is twice the effective height of the supercharger air inlet; to ensure that all the air inhaled by the engine comes from the upper air supply duct, the air flow rate blown to the supercharger inlet should meet v'>7m / s.

[0027] Furthermore, the air supply duct is designed to be inclined downward at 45 degrees, and the airflow along the center line of the air supply port should be directly blown to the center of the height of the supercharger air inlet.

[0028] Furthermore, the overall air volume calculation includes:

[0029] The rated flow rate of a single fan of two outdoor variable frequency fans is Q = q + nq' / 2 [m 3 / h];

[0030] Total flow rate of the exhaust fan on the top of the laboratory Q out ≥2q[m 3 / h].

[0031] Furthermore, the ventilation system effect estimation specifically includes:

[0032] The engine intake air temperature is basically consistent with the outdoor ambient temperature, the intake air temperature of each supercharger is uniform, and the maximum intake air temperature difference T max -T min ≤1℃;

[0033] When the engine is running at rated conditions, the test room temperature rise shall not exceed 5°C, that is, the difference between the indoor and outdoor ambient temperatures is Tin -T out ≤5℃.

[0034] The laboratory ventilation system and optimization design method for a multi-supercharger sequential supercharging engine provided by the present invention have the following beneficial effects compared with the prior art:

[0035] The present invention independently arranges air supply for engine combustion demand and laboratory heat dissipation demand, realizes accurate fresh air supply to the supercharger air intake area and the body heat dissipation area, and effectively simulates the actual cabin air intake environment; proposes a design and calculation method for ventilation flow according to the rated power of the engine, realizes the reasonable allocation of air supply for combustion demand and heat dissipation demand; through simulation calculation, determines the air supply layout form, effectively organizes the airflow, and ensures that each supercharger takes in air at a temperature close to the outdoor environment while achieving a good heat exchange effect; the overall ventilation flow is adjusted according to the test conditions, and the independent air supply in the air intake area is intervened according to the working state of the supercharger, so that similar ventilation effects are maintained under different test conditions, thereby achieving energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram I of the ventilation system of the present invention (main viewing angle);

[0037] Figure 2 Schematic diagram II of the ventilation system of the present invention (top view);

[0038] Figure 3 This is a schematic diagram of the cross-sectional structure of the air supply pipe of the present invention;

[0039] Figure 4 This is a schematic diagram of the arrangement position of the lower air supply pipe of the present invention;

[0040] Figure 5 This is a schematic diagram of the arrangement position of the upper air supply pipe of the present invention. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0042] The present application proposes a test room ventilation system and design method for a multi-supercharger sequentially supercharged engine, which calculates and matches the air supply flow rate according to the rated power of the engine, designs the air supply port according to the number of superchargers, realizes ventilation heat exchange and supercharger air supply during the engine test, and provides additional targeted air supply for the sequentially working superchargers according to the changes in the test conditions, ensures appropriate ventilation under different working conditions, achieves the consistency of the engine intake temperature with the outdoor ambient temperature, and makes the intake temperature of each supercharger uniform, while saving energy consumption.

[0043] The ventilation system of the present invention is arranged as follows:

[0044] Air is supplied at both ends of the engine and exhausted at the top. The fresh air blows through the engine body from a high altitude, and the temperature rises. It diffuses to both sides and then is exhausted upward, which prevents the high-temperature gas from flowing directly through the supercharger area and being sucked in.

[0045] The air outlet is designed in layers and compartments, and each outlet controls the air outlet independently. The lower air supply duct meets the ventilation form of bottom-in and top-out, which is used for indoor heat dissipation; the upper air supply duct accurately supplies air to the supercharger intake area, and cooperates with the superchargers to open one after another.

[0046] like Figure 1 and Figure 2 As shown, the ventilation system includes: air supply ducts arranged at both ends of the engine, exhaust ducts on the top of the test building, a PLC control box, an air supply switching valve, and an outdoor fan.

[0047] The design of the air supply pipe and the air supply control method are described as follows:

[0048] (1) The air supply pipe structure at both ends of the engine is as follows Figure 3 As shown, there are two layers, the upper layer is divided into left and right grids, which are respectively aimed at the air inlets of the superchargers on both sides of the engine, so that the engine can take in air at the outdoor ambient temperature; the lower layer is not divided into grids, and is aimed at the engine body below the supercharger for blowing and heat dissipation, thereby enhancing indoor air flow.

[0049] (2) The lower air supply is fully open, and the upper air supply is automatically opened and closed according to the engine operating conditions. When the supercharger is working, the corresponding upper air supply pipe is also opened to provide targeted air supply.

[0050] The design method of this ventilation system is as follows:

[0051] a) Calculation of lower floor air supply

[0052] The lower air supply is used to purge the engine body to achieve ventilation and heat exchange. Assuming the rated power of the engine is P [kW], the total power of heat dissipation to the test room is φ = 0.1P [kW]. Under rated working conditions, the heat dissipation power is a constant. Heat dissipation is achieved through convection and heat radiation.

[0053] Total heat dissipation power: Φ=Φ1+Φ2

[0054] Convective heat transfer power: Φ1=hA(T1-T2)

[0055] Radiative heat transfer power: Φ2=εAσ(T1 4 -T2 4 )

[0056] The convective heat transfer coefficient h increases mainly with the increase of air flow velocity, while the radiation heat transfer power is determined by the surface temperature of the diesel engine. By increasing the flow rate to increase the h value, φ1 will increase and φ2 will decrease. When the convective heat transfer effect is enhanced, the impact on the surface temperature of the diesel engine will be reduced, thereby reducing the radiation heat dissipation power and reducing the temperature rise in the area far from the engine. Therefore, maintaining a certain flow rate of the purge air on the surface of the diesel engine can ensure that the test room has a good ventilation and heat exchange effect.

[0057] The width of the lower air outlet should be greater than the width of the engine, and the height should be designed to be 1 / 2 of the height of the engine body. The purge air volume at one end of the engine is q≥100φ[m 3 / h], the air velocity when blowing to the engine body v≥7m / s, the air supply pipe is designed to be inclined downward at 45°, and the air flow along the center line of the air supply port should be blown directly to the center of the height of the engine body, such as Figure 4 According to the above principles, the size design of the lower air supply pipe opening is completed, and the appropriate distance between the air supply opening and the engine is evaluated and confirmed through flow field simulation technology.

[0058] b) Upper floor air supply calculation

[0059] The upper air supply pipe is used to meet the air intake demand of the supercharger on the top of the engine. Assume that the number of superchargers is n, the number of upper air supply pipe openings is also n, and the number of upper air supply pipe openings at one end of the engine is n / 2. The air intake demand of a single supercharger at normal temperature is A[m 3 / h], that is, the flow rate of a single air supply pipe on the upper layer q'≥A[m 3 / h].

[0060] The total width of the upper air supply duct is the same as that of the lower duct, the air outlet interval is 0.05-0.1m, and the air outlet height is twice the effective height of the supercharger air inlet. To ensure that all the air inhaled by the engine comes from the upper air supply duct, the air velocity at the supercharger inlet should meet v'>7m / s. The air supply duct is designed to be inclined downward at 45°, and the airflow along the center line of the air supply outlet should be directly blown to the center of the supercharger air inlet height, such as Figure 5 According to the above principles, the size design of the upper air supply duct is completed, and the appropriate distance between the air supply duct and the engine is evaluated and confirmed through flow field simulation technology.

[0061] c) Calculation of overall air volume

[0062] Two outdoor variable frequency blowers are designed. Each blower supplies air to the upper and lower blower pipes at one end of the engine. According to the calculation results, the rated flow rate of a single blower is Q = q + nq' / 2 [m 3 / h]. Total flow rate of the exhaust fan at the top of the laboratory Q out ≥2q[m 3 / h].

[0063] d) Ventilation system effectiveness estimation

[0064] According to the ventilation system designed by the present invention, the engine intake temperature is basically consistent with the outdoor ambient temperature, the intake temperature of each supercharger is uniform, and the maximum intake temperature difference T max -T min ≤1℃. When the engine is running at rated conditions, the test room temperature rise shall not exceed 5℃, that is, the difference between the indoor and outdoor ambient temperatures T in -T out ≤5℃.

[0065] A few points to note:

[0066] 1. The exhaust fan is fixed frequency, the supply fan is variable frequency, and the total air volume of the supply fan is the indoor ventilation demand + the total engine intake air consumption. When the lower air duct is opened, the flow rate corresponding to the operating frequency of the supply fan is the indoor ventilation demand q; when the upper air duct is opened, the engine intake air consumption under this working condition is determined according to the number of supercharger operations, and the supply fan operating frequency increases by a corresponding value.

[0067] 2. After the engine test begins, the switch valve controls the lower air supply pipe to open, and the outdoor air inlet and exhaust fans are turned on to continuously blow and dissipate heat from the engine body. The lower air supply pipe is not closed during the test.

[0068] 3. The PLC control box receives the engine operating condition information in real time, determines whether each supercharger is in working state, and obtains the number (position) of the supercharger in working state.

[0069] 4. For the working supercharger, adjust the switching valve to open the corresponding air supply pipe to supply air to it, so that the supercharger can take in air at the outdoor ambient temperature, and each working supercharger receives an independent and equal amount of fresh air supply, and the intake air temperature is consistent.

[0070] 5. For the supercharger that is not in operation, the corresponding air supply pipe opening remains closed to save energy consumption of the air supply fan.

[0071] In summary, the above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereto. All equivalent changes and modifications made according to the patent scope of the present invention and the contents of the specification are within the scope covered by the patent of the present invention.

Claims

1. A test room ventilation system for a multi-supercharger sequential supercharged engine, characterized in that: It includes air supply ducts arranged at both ends of the engine, the ends of the air supply ducts pass through the test room and are provided with a first outdoor fan; a switching valve is provided between the end of the air supply duct outside the test room and the first outdoor fan, and the switching valve is electrically connected to a PLC control box to realize automatic opening and closing of the air supply duct according to the operating conditions of the engine.

2. The system according to claim 1, characterized in that: The air supply duct is divided into two layers, the lower layer air supply is fully open, and the upper layer air supply is automatically opened and closed according to the engine operating conditions.

3. The system according to claim 2, characterized in that: The upper air supply of the air supply duct is divided into left and right grids, respectively aimed at the air inlets of the superchargers on both sides of the engine; the lower air supply of the air supply duct is not divided into grids, and is aimed at the engine body below the supercharger.

4. The system according to claim 1, characterized in that: It also includes an exhaust duct on the top of the test building, in which a second outdoor fan is arranged.

5. The system design method according to any one of claims 1 to 4, characterized in that: The following steps are involved: Lower air supply calculation: The lower air supply is used to purge the engine body to achieve ventilation and heat exchange; Upper air supply calculation: The upper air supply duct is used to meet the air intake demand of the supercharger on the top of the engine; Calculate the overall air volume and design two outdoor variable frequency blowers to supply air to the air supply pipe at one end of the engine; Estimation of ventilation system effectiveness.

6. The method according to claim 5, characterized in that The calculation of lower-level air supply specifically includes: Assume that the rated power of the engine is P [kW], and the total power of heat dissipation to the test room is φ = 0.1P [kW]. Under rated conditions, the heat dissipation power is a constant value; heat dissipation is achieved through convection and thermal radiation: Total heat dissipation power: Φ=Φ1+Φ2 Convective heat transfer power: Φ1=hA(T1-T2) Radiant heat transfer power: The convective heat transfer coefficient h increases mainly with the increase of air flow velocity, while the radiation heat transfer power is determined by the surface temperature of the diesel engine; if the h value is increased by increasing the flow velocity, φ1 will increase and φ2 will decrease; The width of the lower air outlet is greater than the width of the engine, and the height is designed to be 1 / 2 of the height of the engine body; The purge air volume at one end of the engine is q≥100φ[m 3 / h], the air velocity when blowing to the engine body is v≥7m / s, the air supply duct is designed to be inclined downward at 45°, and the air flow along the center line of the air supply port should be blown directly to the height center of the engine body.

7. The system according to claim 5, characterized in that The upper air supply calculation specifically includes: Assume that the number of superchargers is n, the number of upper air supply pipe openings is also n, and the number of upper air supply pipe openings at one end of the engine is n / 2. The air intake demand of a single supercharger at room temperature is A[m 3 / h], that is, the flow rate of a single air supply pipe on the upper layer q'≥A[m 3 / h]; The total width of the upper air supply duct is consistent with that of the lower one, the air outlet interval is 0.05-0.1m, and the air outlet height is twice the effective height of the supercharger air inlet; to ensure that all the air inhaled by the engine comes from the upper air supply duct, the air flow rate blown to the supercharger inlet should meet v'>7m / s.

8. The method according to claim 7, characterized in that: The air supply duct is designed to be inclined downward at 45 degrees, and the airflow along the center line of the air supply port should be blown directly to the height center of the supercharger air inlet.

9. The system according to claim 5, characterized in that The overall air volume calculation includes: The rated flow rate of a single fan of two outdoor variable frequency fans is Q = q + nq' / 2 [m 3 / h]; Total flow rate of the exhaust fan on the top of the laboratory Q out ≥2q[m 3 / h].

10. The system according to claim 5, characterized in that The ventilation system effect estimation includes: The engine intake air temperature is basically consistent with the outdoor ambient temperature, the intake air temperature of each supercharger is uniform, and the maximum intake air temperature difference T max -T min ≤1℃; When the engine is running at rated conditions, the test room temperature rise shall not exceed 5°C, that is, the difference between the indoor and outdoor ambient temperatures is T in -T out ≤5℃.

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