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EP-4028658-B1 - METHOD FOR DETERMINING THE MASS OF GAS ENCLOSED IN A COMBUSTION CHAMBER

EP4028658B1EP 4028658 B1EP4028658 B1EP 4028658B1EP-4028658-B1

Inventors

  • KASSA, Mateos
  • Leroy, Thomas

Dates

Publication Date
20260513
Application Date
20200902

Claims (7)

  1. Method for determining the enclosed mass of gas in a combustion chamber (2) of an internal-combustion engine, wherein the following steps are carried out: a) the pressure P of said gas in said combustion chamber (2) is measured (MES P); b) the oscillations of said gas pressure P are determined (OSC P) from said pressure measurement P of said gas; c) said enclosed mass m of gas is determined using the formula m = γPV λ 2 f 2 and by determining (DET f) the frequency f of pressure oscillations using said measured oscillations, V being the volume of said combustion chamber, λ the wavelength in said combustion chamber (2), P said measured pressure of said gas in said combustion chamber, and γ the specific heat ratio, the frequency f of pressure oscillations is determined (DET f) by implementing the following calibration steps: i) at least two predefined enclosed masses m 1 , ..., m n of gas are considered; ii) a specific heat ratio γ is determined for each predefined enclosed mass m 1 , ..., m n of gas; iii) said formula m = γPV λ 2 f 2 is used to determine a frequency f of pressure oscillations for each predefined enclosed mass m 1 , ..., m n of gas as a function of said measured gas pressure P, said volume V of the combustion chamber, said wavelength λ and said determined specific heat ratio γ; and iv) each determined frequency f of pressure oscillations is compared (COMP) with said measured pressure oscillations (OSC), and said enclosed mass m of gas is determined as the predefined mass for which the pressure oscillation frequency f minimizes said comparison, said wavelength λ being obtained from a map based on the crankshaft angle of said internal-combustion engine, said map being constructed numerically in advance using a three-dimensional finite element approach.
  2. Method for determining the enclosed mass of gas according to Claim 1, wherein said volume V of said combustion chamber (2) is obtained from a map based on the crankshaft angle of said internal-combustion engine.
  3. Method for determining the enclosed mass of gas according to one of the preceding claims, wherein said map for obtaining said wavelength λ is constructed numerically in advance using a three-dimensional finite element approach with the following inputs: - the geometry of the combustion chamber at each crankshaft angle, - the wave equation to be solved P = 1 c 2 δ 2 P δt 2 with a fixed speed of sound c, - the boundary conditions ∇P.n = 0 , n being the vector normal to the cylinder wall, - the initial conditions: a localized pressure gradient used to initialize the calculation.
  4. Method for determining the enclosed mass of gas according to one of the preceding claims, wherein said specific heat ratio γ is determined by taking into account the composition of said enclosed mass, and by means of the thermal capacity of the components of said enclosed mass.
  5. Method for determining the enclosed mass of gas according to one of the preceding claims, wherein said enclosed mass of gas is determined in real time.
  6. Method for determining the enclosed mass of gas according to one of the preceding claims, wherein each specific heat ratio γ of each predefined enclosed mass m 1 , ..., m n of gas is determined by implementing the following steps: (1) the composition of said enclosed mass is determined; (2) a relationship linking said specific heat ratio γ and the capacity c p of the gas in said combustion chamber is determined: γ = c p c p − R where R is the gas constant, and the capacity c p of the gas being a function of the temperature of said gas and of said composition of said enclosed mass; (3) the temperature of said gas is determined by means of the ideal gas law applied to each predefined enclosed mass m 1 , ..., m n ; and (4) said specific heat ratio γ for each predefined enclosed mass m 1 , ..., m n is deduced therefrom.
  7. Method for determining the enclosed mass of gas according to one of the preceding claims, wherein a wavelength λ is determined for each oscillation mode of said pressure of said gas.

Description

technical field The present invention relates to the field of determining the mass of gas enclosed in a combustion chamber of an internal combustion engine. The mass of gas trapped in a combustion chamber is a useful parameter, particularly for the control and testing of internal combustion engines. It allows for the analysis of combustion, the improvement of combustion control strategies, and the enhancement of cycle-by-cycle and inter-cylinder performance. Knowledge of this parameter is especially important for spark-ignition engines and for diesel engines equipped with exhaust gas recirculation (EGR) and/or variable valve timing. Previous technique No sensor can directly measure the mass of gas trapped in a combustion chamber. Therefore, several methods have been developed to estimate this parameter. However, no method provides reliable information. In particular, some methods are based on intake pressure measurements, which may not reliably represent the physical phenomena occurring within the combustion chamber. Other methods require signal processing techniques that can be complex, time-consuming, and may also introduce inaccuracies in the estimated mass of trapped gas. The patent application WO 2007060349 This method, based on the use of a pressure sensor in the cylinder and a temperature sensor downstream of the exhaust valve, requires specific instrumentation for the internal combustion engine. Furthermore, this method reconstructs the gas temperature in the cylinder from the measurement taken by the temperature sensor downstream of the exhaust valve. This reconstruction generates approximations, which affect the accuracy of the estimated trapped gas mass. The patent application WO 2015082731 describes a method based on estimating the pressure resonance frequency in the combustion chamber using a Fourier transform, which is a signal processing technique applied to the pressure sensor. This estimation of the resonance frequency lacks the precision required for accurately estimating the mass of trapped gas. Furthermore, this method relies on solving Bessel's equations, assuming that the combustion chamber is a perfect cylinder. However, the combustion chambers of internal combustion engines are not perfectly cylindrical. Consequently, the estimate obtained using this method is inaccurate due to this assumption. In addition, this method requires oscillations of significant amplitude. The thesis of Pau Bares "In-cylinder pressure resonance analysis for mass trapped estimation in automotive engines" (June 30, 2017 (2017-06-30 ), Valencia) discloses a calculation of the mass of air and fuel in the combustion chamber. Summary of the invention The present invention aims to accurately determine the mass of gas trapped in the combustion chamber of an internal combustion engine, using simple and conventional instrumentation and without complex signal processing. To this end, the method for determining the mass of gas trapped in a combustion chamber according to the invention is based solely on measuring the pressure within the combustion chamber. The method employs a model of the combustion chamber, one parameter of which, the pressure oscillation frequency, is determined by measuring the gas pressure in the combustion chamber. Thus, the method according to the invention is accurate, reliable, and requires simple instrumentation. The invention according to claim 1 relates to a method for determining the mass of gas enclosed in a combustion chamber of an internal combustion engine, in which the following steps are carried out: a) The pressure P of said gas is measured in said combustion chamber; b) The oscillations of said gas pressure P are determined from said pressure measurement P of said gas; c) The mass of enclosed gas m is determined using the formula m=γPVλ2f2 and by determining the oscillation frequency f of pressure with said oscillations measured, V being the volume of said combustion chamber, λ the wavelength in said combustion chamber, P said measured pressure of said gas in said combustion chamber, and γ the specific heat ratio. According to one embodiment, said volume V of said combustion chamber is obtained by means of a mapping as a function of the crankshaft angle of said internal combustion engine. According to the invention, said wavelength λ is obtained by means of a mapping as a function of the crankshaft angle of said internal combustion engine. According to the invention, said mapping of said wavelength λ is constructed beforehand digitally. According to the invention, said mapping of said wavelength λ is constructed by a three-dimensional finite element approach. According to one aspect of the invention, said specific thermal ratio γ is determined by taking into account the composition of said enclosed mass, and by means of the thermal capacity of the components of said enclosed mass. In accordance with a characteristic, the said mass of gas enclosed is determined in real time. Accordi