Combustion Diagnostics by Means of Multizone Heat Release Analysis and NO Calculation

Abstract

In this paper a combustion diagnostic method is presented where measured pressure data is used to calculate the heat release, local temperatures and concentrations of NO and other species. This is done by a multizone model where the lambda value, i.e. 1/equivalence ratio, in each zone can be chosen arbitrarily. In homogenous charge engines lambda is given by the global air/fuel ratio. The local lambdas during initial combustion in stratified charge and diesel engines have to be estimated either as an average value or with a chosen distribution.One new zone of each local lambda is generated and the temperature, volume and species in all old zones are updated at each time step of calculation. In this paper the model is demonstrated by using pressure data from premixed and direct injected stratified charge natural gas SI engines and from a DI diesel engine.The pre-mixed data is used to validate the model as such while the ambition in the stratified charge and diesel cases has been to find the average local lambda that gives the same NOx emission as measured. The emphasis in the latter cases has been to study the influence on average local lambda of the duration of the fuel injection. Early injected fuel seems to burn at slightly leaner mixtures than later injected.

A Fast Physical NOx Model Implemented on an Embedded System

“…The local air/fuel ratio, λ, must also be known. Knowing the exact local λ is difficult, λ cal is hence introduced as a tuning parameter in the model in a fashion similar to [4], hence combustion is assumed to take place at a constant λ.…”

“…(3), similarly to [4] and [2]. The temperature and pressure datum (T g0 and P g0 ) used to compute the temperature of the unburned zone is acquired just before the combustion has started to reduce the effect of losses, e.g.…”

“…The claim of [2] is "real-time" performance of the model, the platform was however a (for the time) high-spec desktop computer, avoiding many of the obstacles present in on-board computation systems. Another contribution in the area is given by [4] on which the model part of this paper (as well as the work of [2] and [3]) is based. The major difference between this model and [4], who utilizes conservation of energy iteratively to find a burned zone temperature, is the observation that it is possible to indirectly compute the temperature of the burned and unburned zones (provided that a two-zone approach is used).…”

“…Another contribution in the area is given by [4] on which the model part of this paper (as well as the work of [2] and [3]) is based. The major difference between this model and [4], who utilizes conservation of energy iteratively to find a burned zone temperature, is the observation that it is possible to indirectly compute the temperature of the burned and unburned zones (provided that a two-zone approach is used). The computation of the burned zone temperature is hence exchanged for a physically correct computation which does not require iterations.…”

Combustion Characteristics of Methane in A Direct Injection Engine Using Spark Plug Fuel Injector

“…In these models, the effect of wall heat transfer and mass flux across the system boundary are taken into account. Other models take into account two zones contributing to combustion process; unburned and burnt zones (Egnell 1998& Geuzennec 1999. These methods that use pressure history are subjected to some errors due to incorrect absolute pressure referencing, thermal shock, measurement error from the pressure transducer, amplifier system calibration error, inaccurate crank angle phasing.…”