Glow Plug Temperature Estimation via Cylinder Pressure
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Solution Overview
Problem
Current methods for estimating the temperature of glow plugs in diesel engines are inaccurate due to reliance on measured cylinder pressure and lack of precise estimation of gas temperature within the combustion chamber, leading to potential overheating and reduced engine starting efficiency.
Innovation Solution
A method and system for estimating the temperature of glow plugs using cylinder pressure sensors and physical parameters, such as crankshaft position, cylinder volume, and polytropic compression coefficients, to calculate the temperature at various engine cycles, eliminating the need for temperature maps and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional temperature estimation methods using only cylinder pressure are used, then the system complexity is low, but the temperature estimation precision is insufficient
Solution Approach 1:
The patent transforms the temperature estimation problem by changing from direct measurement to indirect calculation through multiple parameters. It uses cylinder pressure measurements combined with polytropic compression models, heat transfer coefficients, and energy balance equations to compute glow plug temperature, thereby achieving high precision without adding complex hardware sensors.
2Reliability
If the glow plug temperature is not accurately monitored, then the control system is simple, but the glow plug may overheat and get damaged
Solution Approach 1:
The patent implements a feedback mechanism where the calculated glow plug temperature is continuously fed back to the control unit. This feedback enables real-time monitoring and adjustment of heating power, allowing the system to prevent overheating and protect the glow plug without requiring complex additional sensing hardware.
3Productivity
If the heating power is increased to improve engine starting, then the engine starting efficiency is improved, but the glow plug temperature may exceed maximum allowable temperature
Solution Approach 1:
The patent employs dynamic control of the heating power based on real-time temperature calculations. The control unit continuously adjusts the electrical power supplied to the glow plug according to the calculated temperature and engine operating conditions, enabling the system to maximize heating effectiveness for cold starts while dynamically preventing temperature from exceeding safe limits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a robust and precise estimation of glow plug temperature, enhancing engine starting and stability by accurately controlling the heating process, regardless of engine operating conditions.
Implementation Method 1
The energy gained E gained is written according to the following equation and corresponds to the electrical power applied to the spark plug. With: U, the voltage applied to the spark plug, expressed in V; I, the intensity traversing the candle, expressed in A; and R, the resistance of the candle varying in a linear way according to the temperature of the candle
Implementation Method 2
The lost energy E lost is written according to the following equation and corresponds to the cooling by convective exchanges with the gases internal to the combustion chamber... h, a heat exchange coefficient varying linearly as a function of the gas temperature in the combustion chamber
Implementation Method 3
The lost energy E lost is written according to the following equation and corresponds to the cooling by convective exchanges with the gases internal to the combustion chamber, and by conduction between the spark plug and its mounting on the cylinder head of the engine... λ, the thermal conductivity expressed in W /(m 2)
Data Source
Figure 1~2
AI summary
Method (20) for estimating the temperature (T(t)) of the glow plug pencil located in a combustion chamber of an internal combustion engine, in particular of the Diesel type, comprising at least one cylinder pressure sensor (Pcyl), wherein by measuring the cylinder pressure (Pcyl), for each crankshaft position, knowing the glow plug pilot voltage, initializing the glow plug temperature (T(t)) at the first calculation step cold engine, at the cylinder head temperature, or at the previous temperature in case of hot start, an average temperature value in the cylinder is estimated over a combustion cycle (Tgas(cycle)) and by iterative calculation steps, the temperature (T(t)) of the glow plug pencil is estimated.