Horsepower Lab 1D" (or simply hpl1d) software package is designed to simulate unsteady gasdynamical phenomena in engines and other "pipelined" facilities using 1D formulation of gasdynamic problems.

Modular approach is utilized in this package: typical elements of system modeled are represented by modules comprizing an Assembly that describes some specific setup. Two kinds of modules used: Components and Connectors.

Component is such kind of module that contains the fluid (generally, any resource or conserved quantity) and is responsible for updating the flow parameters. Examples are: Atmosphere component that simply contains ambient parameters, Vessel that accounts for thermodynamics of vessels (or "tanks") with gaseous fluid, component Duct that models unsteady flow of gaseous mixture in duct, Cylinder that can simulate processes in engine's combustion chamber and so on.

To better simulate unsteady flow in Duct, which evolves in space and in time, high resolution numerical scheme is used. This method approximates 1D gas dynamics conservation laws to higher order of accuracy and gives monotone solutions.

Connector -- another kind of module -- serves to evaluate instantaneous interactions between components (computes fluxes of resources in general). Connectors types (implemented to date in hpl1d) are Restriction (with 3 sub-types: Diaphragm, Valve and Window) and Splitter (with 2 sub-types: Triple and Chink). Connector Restriction links one component to another, whereas the (flow) Splitter interconnects 3 gasdynamic components.

As for the models incorporated in connectors -- models are based on a generalized Riemann problem. Model of this class meets the requirement to insure correctness of the internal boundary conditions for Duct component, when linked to. The only exception is Window connector, which is not linked to any Duct, and for which the model of quasi-stationary discharge is used.

Solver of the package is written in C and so it can be easily compiled and run under virtually any computer platform. Solver starts with reading initial data from the human-readable input file and performs several outputs into different specified file streams. It can simulate 2- and 4-stroke engines with single or multiple cylinders, along with non-engine pipeline-like installations.

All operation is done on projects that consist of specific engine (or maybe some other installation) setup and additional data such as the thermodynamic properties of gaseous working fluids and some data tables of properties of connectors, etc.

Numerical scheme used for solver (simulator) integrates models' differential equations with 2nd order of accuracy in time, and the 1D unsteady gas dynamic conservation laws are discretized by quasi-3rd-order in space monotone conservative finite-volume numerical scheme.

GUI to the package now (as of v. 0.95) is provided by a standalone program hpl1dw.exe (written in C with pure Win32 API). GUI helps much to manage the projects. Click here to load screenshots page for the current version of hpl1d.

Older versions had their own GUIs. Screenshots on Fig. 1 and 2 give the idea what it looked like under Linux (KDE2 desktop environment). It was written in Java, using AWT widget set (early 2000s).