Natural Gas Compression System with Two-Stage Induction
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Solution Overview
Problem
Natural gas engines face challenges in maintaining constant torque over a wide range of engine speeds due to elevated exhaust temperatures and backpressure caused by turbochargers, limiting their performance and efficiency, especially in applications like pipeline gas compression where speed turndown is necessary.
Innovation Solution
A natural gas compression system incorporating a two-stage induction system with a supercharger and turbocharger, along with a supercharger compressor bypass and turbo compressor bypass, allows for selective recirculation of compressed air to manage intake charge pressure and maintain constant torque output across varying engine speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a turbocharger is used to improve low rpm power/torque output, then boost is increased, but at higher rpm the turbo creates high backpressure requiring detuning
Solution Approach 1:
The induction system is segmented into two independent stages: a supercharger for low-rpm operation and a turbocharger for high-rpm operation. Each compressor handles a specific operating range, allowing both to be optimized for their respective functions without compromising the other. The system can operate with one or both compressors depending on engine speed requirements.
Solution Approach 2:
The patent implements a nested configuration where the turbocharger compressor is positioned downstream of the supercharger compressor in the induction system. This allows the supercharger to provide initial compression that reduces the work required by the turbocharger, creating a cascaded compression system that efficiently covers a broad operating range.
2Power
If a turbocharger is used to improve performance, then boost is increased, but exhaust temperatures are elevated limiting potential performance improvements
Solution Approach 1:
The compression function is segmented between a mechanically-driven supercharger and an exhaust-driven turbocharger. The supercharger handles low-rpm compression without adding backpressure to the exhaust system, while the turbocharger handles high-rpm compression. This segmentation allows the turbocharger to be detuned or bypassed at low rpm, preventing unnecessary exhaust temperature elevation.
Solution Approach 2:
The system dynamically switches between supercharger-dominated operation at low rpm and turbocharger-dominated operation at high rpm. Control mechanisms adjust the contribution of each compressor based on engine speed and load conditions, optimizing performance while managing exhaust temperatures across the entire operating range.
3Speed
If engine speed is reduced to allow speed turndown in compression applications, then compressor speed is reduced, but torque output must be maintained constant
Solution Approach 1:
The dual-compressor system ensures continuous optimal compression across the entire engine speed range. At low engine speeds, the supercharger maintains adequate intake charge pressure that would be insufficient with a turbocharger alone. This continuity allows the engine to maintain constant torque output during speed turndown operations without losing compression efficiency.
Solution Approach 2:
The system changes the dominant compression mechanism based on engine speed parameters. At low speeds, mechanical supercharging provides the necessary torque multiplication. At high speeds, exhaust-driven turbocharging takes over. This parameter-based switching allows constant torque maintenance across a broad speed range, enabling effective speed turndown for pipeline compression applications.
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 configuration reduces exhaust temperatures, minimizes backpressure, and enables the engine to maintain constant torque output over a broad range of speeds, enhancing performance and efficiency, particularly at higher rpm and high altitudes, while allowing for controlled speed turndown in gas compression applications.
Implementation Method 1
a supercharger driven by the engine and configured to compress intake air
Implementation Method 2
a turbocharger downstream from the supercharger and driven by exhaust gases produced by the engine
Implementation Method 3
a natural gas burning engine used to drive the compressor
Data Source
AI summary
A natural gas compression system is provided. The system may include a natural gas compressor configured to compress, and thereby pump, natural gas through a pipeline. The system may also include a natural gas burning engine, operatively coupled to the gas compressor, the engine being supplied with air by an induction system. The induction system may include a supercharger driven by the engine and configured to compress intake air and a turbocharger downstream from the supercharger and driven by exhaust gases produced by the engine. The induction system may also include a supercharger compressor bypass configured to selectively recirculate a portion of the compressed output of the supercharger upstream of the supercharger.