Engine Simulation Software: EngMod2T

EngMod2T

Detailed Description

Engine Layouts

The current version of the software can simulate engines ranging from 1 to 8 cylinders with the following layouts:

Inline Engine
Vee Engine
Boxer Engine with a choice of common or separate crankcases
Opposed Piston Engine with a choice of crankcase or external scavenging
Radial Engine
Uniflow engine with poppet exhaust valves
Boosted Engine with poppet inlet and poppet exhaust valves
Reverse Uniflow Engine with poppet inlet valves and window type exhaust port

Two versions of scavenging / inlet systems are available:

Crankcase scavenging - the tradisional inlet into crankcase and then into the cyllinders via the transfer ports
External scavenging - used in conjunction with a turbo- or supercharger where the pressurized inlets are directly into the cylinders

It has built in calculators for basic head shapes, crankcase compression ratio and target BMEP

Types of Inlet Systems

The following is a brief summary of the available inlet systems:

Separate Inlets

Separate inlets with a common air box

Manifold Inlet Systems

All intakes can have: Throttle valves and/or boost bottles

Types of Inlet Ports

Reed Valve - Case Reed

Reed Valve - Cylinder Reed

Reed Valve plus Piston Port

Piston Port

Rotary Disc Valve

Rotary Shaft Valve

Rotary Drum Valve

Poppet Valve Inlet

EngMod2T is one of the very few programs that model cylinder reed valves correctly with a combination of cylinder ports, Boyesen ports and floor ports.

Scavenging Model

The scavenging model is based on the Blair model with some refinements. It is based on measurements in a special type of test apparatus.

Transfer Ports

The software can model from 2 to 12 ports

There is also an option to model the geometry of the transfer port ducts into the cylinder

Combustion Modeling

Two types of combustion modeling is available and both are based on the typical two-zone model (a burnt and an unburnt zone):

Prescribed combustion depending on user input like the Vibe (Wiebe) values and the delay and combustion duration periods.

Turbulent entrainment combustion which uses turbulence modeling and mass entrainment into the flame front to model the combustion process.

Exhaust Ports

The exhaust ports fall into four main classes:

Single Main Window with/without auxiliary ports
Bridged Main Window with/without auxiliary ports
Arbitrary shape port modelled as a user defined profile
Poppet Valve operated by a camshaft

The first two types also has the option of having a powervalve. The powervalve can be of the governor type (mechanical or servo motor) or of the pneumatic type. It can be in the main port only or also in the auxiliary ports. The auxiliary port powervalve can be controlled by the main powervalve or separately.

Exhaust Systems

The available exhaust systems fall into three main classes:

Single Pipe per cylinder
Branch manifold
Log manifold

Each class can be further divided into the following types:

Tuned pipe - the main or collector pipe can be configured as a tuned pipe.
Open pipe - the main or collector pipe can be configured as an open pipe
Box pipe - the main or collector pipe has a box or plenum in it.
Silencer pipe - any one of the above pipes can terminate in a silencer.
Perforated Rear Cone - The Tuned Pipes and Open Pipes can terminate ina perforated rear cone.

The pipes can also be fitted with a controlled resonating chamber commonly know as an ATAC system.

There is also a utility that can generate a tuned pipe based on one of the following 4 models:

Blair pipe - the pipe is based on the guidelines as presented by the late Prof GP Blair.

FOS pipe - the pipe is based on the guidelines as presented by Frits Overmars.

Modern pipe - the pipe is based on the multi diffuser layout as was state of the art in the early 1990's.

High Performance pipe - the pipe is based on the state of the art as it is currently.

Wall and Atmosheric Temperature and Atmospheric Pressure

The wall temperature for each duct, plenum, cylinder, head, bore, piston crown, crankcase or box is entered.

The exhaust system wall temperature can be entered as a single value or as a function of engine RPM and / or of pipe position.

The atmospheric temperature and pressure for the inlet and exhaust can be separaely entered.

Supercharger Modeling

The current release allows for the modeling of a single supercharger with or without Charge air cooler (intercooler). Software is included to digitize the compressor characteristics. It can be either a centrifugal compressor or twin rotor type compressor (eg Roots).

Turbocharger Modeling

The current release allows for the modeling of a single turbocharger with or without Charge air cooler (intercooler) and wastegate. Software is included to digitize the compressor and turbine characteristics.

The exhaust system can be modelled as straight pipes or tuned pipes. The figure shows three of the tuned pipe options available for an I4 engine.

Some of the Tools included in the modeller Dat2T:

As part of the pre-processor, Dat2T, there is a utility to verify the port window design but it requires the scavenging port model as input:

Also part of the pre-processor, Dat2T, there is a utility to verify the Specific Time Area (STA) design:

There is also a utility to verify the Pipe, Port and Duct design:

And it also has a utility to update the port timing by lifting or lowering the complete cylinder:

Example of the turbocharger maps in the graphing utility Post2T:

To use a compressor map as part of the simulation it has to be extrapolated into the surge region and to the negative (reverse) flow region. The following is an example of such a digitized and extrapolated map:

To use a turbine map as part of the simulation it has to be digitized. As it is very difficult to obtain a full turbine map, the software currently uses an approximation known as the "swallowing curve". The following is an example of such a digitized swallowing curve: